Page:Natural History Review (1861).djvu/321

Rh named the superior temporal or marginal, 7,7, the middle temporal, 8,8, and the inferior temporal, 9. The convolution of the hippocampus major is marked * in fig, 2. The Island of Reil has five shallow convolutions.]

"We have already stated that the occipital lobe, O, is very large. It presents several parallel sulci, amongst which the one which separates the middle occipital convolution, 11, from the superior occipital convolution, 10,10′, predominates. The operculum, [viz. the border in front of 10,10′], is entire and well developed.

"But the chief ground of distinction between the brains of the Chimpanzee and Orang is the absence [in the Chimpanzee] of the superior connecting convolution (le premier pli de passage).

"Thus, the first or superior connecting convolution is absolutely wanting. [This, if present, would pass across the operculum opposite to 10, fig. 5].

"The second connecting convolution is hidden under the operculum. [This lies opposite to 10′].

"The third, fig. 4, C, and fourth, D, connecting convolutions are superficial."

From the foregoing quotations, it will be seen that the arrangement of the convolutions in our specimen, coincides remarkably with the description of M. Gratiolet. It must be noted, however, that all those on the vertex, are considerably broader and flatter than in the restored figure given by that author; but they resemble in this respect, very strikingly, those represented in Schroeder van der Kolk's and Vrolik's plate. This flatness, evidently the result of pressure, affords a special confirmation of the view that the brain figured by the Dutch anatomists, like our own specimen, had been deformed during its preservation.

Of the convolutional characters which, in M. Gratiolet's opinion, distinguish the Chimpanzee, viz., the great size of the occipital lobe, the neatness of definition of its operculum, the mode of origin of the bent convolution, the absence of the first connecting convolution, and the hidden position of the second, all are strictly fulfilled upon the left cerebral hemisphere of our specimen; but, on the right or dissected side, of which a photograph is preserved, there was a rudimentary superior connecting convolution, of very small size, passing from the outer margin of the lobule of the second ascending convolution, outwards, and then, bending inwards and backwards, across the perpendicular fissure, to join the occipital lobe. The presence of this superior connecting convolution in the Chimpanzee, and on one side only, is another example of that variety and want of symmetry, as regards these connecting convolutions, noticed by Dr. Rolleston in his interesting paper (p. 212). Nevertheless, vary as they may, the several connecting convolutions are evidently, as M. Gratiolet first pointed out, the traces, or homologues, of much more highly developed, but corresponding, parts of the Brain in man. On the whole, too. the evidence is still in favour of this particular connecting convolution being less developed in the Chimpanzee, than in the Orang. As to the second connecting convolution, it existed on both sides of the Chimpanzee's brain, concealed under the operculum, but of good size. In reference to what M. Gratiolet describes as a very remarkable feature in the Chimpanzee's brain, viz., the broad origin of the bent convolution (pli courbe) in front of the top of the Sylvian fis-